Electric or electronic parts such as semiconductor chips mounted on various equipment such as personal computers or power equipment generate heat in some extent when used. When the electric or electronic parts are excessively heated by the generated heat, the performance thereof is lowered, or the lifetime thereof is shortened. Furthermore, since the size of the electric devices represented by the personal computer or the like becomes smaller, it becomes an urgent task to develop an excellent cooling techniques to cool the small-sized electric or electronic parts mounted on the personal computer or the like.
There is provided an air cooling type cooling method as one of the method of cooling electric or electronic elements which is to be cooled (hereinafter referred to as the "part to be cooled"). More specifically, in the air cooling type cooling method, a fan or the like is installed in the box to accommodate the electric devices on which the parts to be cooled are mounted, and the inside of the box is cooled by the fan or the like so as to prevent the temperature of the parts to be cooled from being excessively risen. The above-mentioned cooling method is particularly effective to cool the relatively large-sized electric devices. However, the above-mentioned cooling method is not appropriate to cool the small-sized electric devices.
In addition to the above-mentioned air cooling type cooling method, there is another widely used cooling method in which a heat sink or fin or the like is connected to the parts to be cooled. In the cooling method, the heat of the parts to be cooled is dissipated through the heat sink. In addition, there is a cooling system in which a heat pipe is installed between the parts to be cooled and the heat sink or fin to improve effectiveness of the heat dissipation. Furthermore, there is developed a technique to attain further improved cooling efficiency in which air is blown to the heat sink, fin or the like by an electrically driven fan.
Heat pipe includes a container having a hermetically sealed hollow portion, i.e., cavity therein. The heat pipe has a function in which a heat is transferred from a heat absorbing portion to a heat dissipating portion, which is apart each other, by means of phase transition and movement of a working liquid accommodated within the hollow portion.
There is a round pipe type heat pipe which is widely used. Recently, a plate type heat pipe comes to attract attention. The plate type heat pipe may be called as a flat type heat pipe, a flat plate type heat pipe or the like. The plate type heat pipe has such a superior feature that the parts to be cooled can be effectively cooled, since the parts to be cooled can be contacted with the container in wide area depending on the shape of the container.
As described above, the plate type heat pipe has the superior feature in which the parts to be cooled is contacted in wide area with the heat absorbing surface of the container. In order to secure the flows of the working liquid from the heat dissipating portion to the heat absorbing portion, i.e., flowing back of the working liquid in the plate type heat pipe having the above-mentioned feature, it is preferable to use the heat pipe in so-called bottom heat mode (namely, the mode in which the heat pipe is used with the heat absorbing portion positioned below the heat dissipating portion).
Accordingly, the heat pipe is preferably installed in such manner that the plate type heat pipe is placed with the heat absorbing surface faced downward, and then, the parts to be cooled is contacted with the heat absorbing surface of thus placed heat pipe, and then, the heat sink is provided on the heat dissipating surface which is positioned upper side of the heat pipe. The above-mentioned installation of the heat pipe in relation to the parts to be cooled is the most ideal installation. According to the above installation, the lower side of the plate type heat pipe becomes the heat absorbing surface, and the upper side of the plate type heat pipe on which the heat sink is provided becomes the heat dissipating surface, thus the plate type heat pipe of the so-called bottom heat mode is obtained.
However, the size of the computer or the like becomes remarkably smaller. Together with the downsizing of the computer or the like, the electric or electronic devices mounting the parts to be cooled is installed not only in a fixed manner (for example, is placed on the desk), but also in a mobile manner (for example, is carried by human being). More specifically, the portable type of electric or electronic apparatus is widely used. In particular, it is considered that the small sized computer is to be used under the condition in which the heat pipe is kept inclined. In view of the above situation, it is expected to be provided the plate type heat pipe excellent in cooling efficiency even in case that the heat absorbing surface is positioned above the heat dissipating surface, i.e., the relative vertical position of the heat absorbing surface to the heat dissipating surface is reversed (which is called as the so-called "top heat mode").
The object of the present invention is therefore to provide plate type heat pipe excellent in cooling efficiency even in case of the so-called top heat mode, the method of manufacturing same and a cooling apparatus using the plate type heat pipe.